Question

Suppose that the log-ons to a computer network happened on average twice per minute.

1. What is the mean time between counts?

1. 20                 b) 30 s                    c) 20 s                       d) 15

2. What is the probability that the next log-on will occur after 60 seconds?

1. 0.1353           b) 0.2231                 c) 0.5578                     d) 0.8647

3. What is the probability that the next log-on will occur in the next 60 seconds?

1. 0.2231           b) 0.5578                 c) 0.3347                     d) 0.8647

Answer 1

a) As the number of log ons is twice per minute on an average, therefore the average time between them is computed here as:

= 1/2 min

= 30 sec.

Therefore 30 sec is the required average time here.

b) The probability that the next log on will occur after 60 seconds is computed here as:

= Probability of no logon in the next 1 minute.

This is computed using poisson probability function as:

= e-2 = 0.1353

Therefore 0.1353 is the required probability here.

c) Probability that next log on will occur in the next 60 sec

= 1 - Probability of no logon in the netx 60 sec

= 1 - 0.1353

= 0.8647

Therefore 0.8647 is the required probability here.